[Info-vax] V/I64 R/W USB mass storage boot support?

[Paul Sture]

On Mon, 07 Nov 2011 13:40:35 +1030, Jeremy Begg wrote:

> Rod,
> 
>> I was hoping to be able to use the booted USB mass storage device in
>> R/W mode if possible.
>> 
>> If someone with deeper knowledge of the OpenVMS USB driver indicated
>> that
>> functionality is doomed to fail, then I can explore alternatives.
> 
> I too have successfully booted my rx2600 from a USB stick but I have not
> tried to run VMS from it.  (By "run" I mean do things other than those
> provided by the OpenVMS installation DVD menu.)

That's a good data point.
 
> There's no problem writing to these devices from VMS in the usual way
> (e.g. BACKUP/IMAGE or other RMS file I/O) but I think the VMS kernel
> uses a different code path for writing errorlog buffers and the system
> crashdump file.  It wouldn't surprise me if that code path made various
> assumptions about the device it was writing to.  Hence the failure when
> you tried to shut down the system.  Given that you were then unable to
> boot from the USB stick I would guess that the shutdown failure caused
> the USB stick to get confused about the I/O states.

Yes, the code responsible for writing the dump file is relatively 
primitive. If the rest of the system cannot be trusted as in the case of 
a crash, then it has to be.  This is why a reboot is required to map to a 
new version of a dumpfile.

Those with experience of earlier versions of VMS will recall that it was 
possible to create a new version of the dump file and purge the old one, 
but the code writing the dump would write to the location of the 
original, and much grief would ensue.

> I wouldn't expect VMS to support USB for anything other than booting a
> clone of the installation DVD and performing operations under the
> "single-user" mode that is provided by that DVD.  Which caters for most
> situations except when network access of some sort would be handy.
> 

As with an installation DVD, it's probably possible to tailor your own 
for extra features, but it requires care and patience.

-- 
Paul Sture

"The trouble with quotes on the internet is that it's difficult to
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